The present invention relates to a resinous composition for coating applications, and more particularly relates to a multicomponent resinous coating composition that comprises a curing system that contains hydroxyl groups protected in the form of siloxy groups and contains isocyanate group, in which system alkoxysilyl groups are introduced. The resinous compositions according to the present invention are suitable for use in refinishing automobiles.
At the present time, in the field of refinishing of automobiles, two-package coatings have been widely used that are composed of the combination of an acrylic polyol and a multifunctional isocyanate curing agent to provide room temperature setting property, desired finish, and weatherability characteristices. However, the two-package types have problems such as poor practicable application because of the necessity of blending the main agent and curing agent in the place of the coating operation, the influence of too much or too little blend ratio of the curing agent reflected in the coating performance, and the necessity of a large amount of diluting solvent because of the high viscosity of the base resin due to the hydrogen bond of hydroxyl groups. For the purpose of overcoming these problems, one-package resinous compositions using a vinyl polymer that contains siloxy groups, in place of a vinyl polymer that contains hydroxyl groups, and a multifunctional isocyanate curing agent have been proposed (for example, Japanese Laid-open Patent Nos. 3-250016/1991 and 1-96264/1989). However, such resinous compositions are insufficient for curability at room or lower temperature and cannot satisfy the requirement of refinishing automobiles where quick drying is necessary
Furthermore, improvement of the acid resistance has been required recently since the coating damage by acid rain has become a problem. The system mentioned above combining hydroxyl groups or siloxy groups with a multifunctional isocyanate curing agent has insufficient acid resistance and does not perform satisfactorily.